Power Supplies AC/DC - DC/DC

Regulated DC power supply Notes This PSU has been especially designed for current-hungry ham radio transceivers. It delivers safely around 20Amps at 13.8V. For lower currents, a separate current limiting output, capable of 15ma up to a total of 20A has been added. The power transformer should be capable to deliver at least 25A at 17.5 to 20V. The lower the voltage, the lower power dissipation. The rectified current will be "ironed" by C1, whose capacity should not be less than 40.000uF, (a golden rule of around 2000uF/A), but we recommend 50.000uF. This capacity can be built up by several smaller capacitors in parallel. The base of this design is a simple 12V regulator (7812). The output voltage can be brought to desired value (here 13.8V) by two external resistors (R5 and R6) using this formula: U= 12(1+R5/R6) The low currents (here 15mA) will keep the 7812 in its regular function. As soon as the current rises over 15ma, the voltage drop on R4 will "o

Description This is an add-on Over Voltage Circuit for the LM317 Regulator Circuit subhttp://www.blogger.com/img/blank.gifmitted by Matthew Hewson. The original circuit may be viewed here . Notes It is a voltage regulator that allows a 6v portable supply to be derived from the 12v car battery. You can add a 6.2V zener diode and a LED to warn you when the input supply is overvoltage. If you could find a relay that would operate from 6.2v right up to 12v that you could connect in such a way that if over voltage occurred, then the relay would automatically switch off the output preventing damage to any connected equipment. Such a relay would be quite difficult to find, so I designed this, it is a simple two transistor circuit which will switch off the output should the voltage raise above 6.2v (this can be changed by selecting a different value of zener diode ). Components are as follows: ZD1 =3D 6.2v Zener diode (you can change this to any value, the circuit will

Description This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply. In the event of electrical supply line failure the battery takes over, with no spikes on the regulated supply. Notes This circuit can be adapted for other regulated and unregulated voltages by using different regulators and batteries. For a 15 Volt regulated supply use two 12 Volt batteries in series and a 7815 regulator. There is a lot of flexibility in this circuit. TR1 has a primary matched to the local electrical supply which is 240 Volts in the UK. The secondary winding should be rated at least 12 Volts at 2 amp, but can be higher, for example 15 Volts. FS1 is a slow blow type and protects against short circuits on the output, or indeed a faulty cell in a rechargeable battery. LED 1 will light ONLY when the electricity supply is present, with a power failure the LED will go out and output voltage is maintained by t

Description: I constructed this voltage regulator to power my two way mobile radio from the car cigarette lighter circuit. It has many other uses and the voltage can easily be adjusted by the use of a potentiometer. The voltage regulator is an LM317T, and should accept up to about 14 volts without problems. It can handle up to 1 amp, but you WILL need a heatsink on the voltage regulator The components are R1: 270R R2: 2K Cermet or carbon preset potentiometer C1: 100nF C2: 1uF tantalum LM317T Voltage regulator Heatsink PCB board I also added DC power jacks for input and output on my voltage regulator, a green power LED, and a red over-voltage LED. The over voltage LED uses a zener diode to switch on the LED at a certain preset voltage, this can be varied depending on the voltage of the zener diode, I used a 6.2v zener diode. If you plan to vary the voltage for the different items you power, don't bother adding this feature. If you only plan to use items that run on o

Description: This circuit will generate a smaller DC output voltage from a larger DC input voltage.It is quick and simple to make and by changing the value of the zener diode, the circuit can be universally adapted to provide other output voltages.The circuit and all diagrams represent a DC convertor with 12V battery input and 9Volt DC output. The output voltage is equal to the zener diode voltage less 0.7 volts, or :- Vo = Vz - 0.7 where V z is the value of the zener diode. With the 10V zener diode as shown in the diagram the output voltage is about 9.3 Volts DC. The supply voltage used must always be at least a few volts higher than the zener voltage. In this example I have used a 12 Volt DC battery to provide the regulated 9 Volt DC output. The above graph shows how the output is affected by input voltage variations. This was produced with a load current of 100mA and using a 10 volt rated zener diode. Note that the circuit falls sharply out of regulation when t

Notes controlling the output voltage from a regulator can be made variable in three ways:- 1. Using a fixed reference zener diode to increase the output by the value of the zener 2. A variable resistor for variable output, note that a voltage less than the nominal regulator is not possible 3. A chain of diode such as 1N4001, this increases the output by +0.7 V for every diode used.

Web-masters Note: I have had several requests for a power supply project without using a powehttp://www.blogger.com/img/blank.gifr supply. This can save the expense of buying a transformer, but presents potentially lethal voltages at the output terminals.Under no circumstances should a beginner attempt to build such a project. Please also read the Disclaimer on this site. Important Notice Electric Shock Hazard. In the UK,the neutral wire is connected to earth at the power station. If you touch the "Live" wire, then depending on how well earthed you are, you form a conductive path between Live and Neutral. DO NOT TOUCH the output of this power supply. Whilst the output of this circuit sits innocently at 12V with respect to (wrt) the other terminal, it is also 12V above earth potential. Should a component fail then either terminal will become a potential shock hazard. Below is a project by Ron J, please heed the caution above and Ron's design notes. MAINS ELECTRI

Description: A simple 5 Volt regulated PSU featuring overvoltage protection. Notes The 5 volt regulated power supply for TTL and 74LS series integrated circuits, has to be very precise and tolerant of voltage transients. These IC's are easily damaged by short voltage spikes. A fuse will blow when its current rating is exceeded, but requires several hundred milliseconds to respond. This circuit will react in a few microseconds, triggered when the output voltage exceeds the limit of the zener diode. This circuit uses the crowbar method, where a thyristor is employed and short circuits the supply, causing the fuse to blow. This will take place in a few microseconds or less, and so offers much greater protection than an ordinary fuse. If the output voltage exceed 5.6Volt, then the zener diode will conduct, switching on the thyristor (all in a few microseconds), the output voltage is therefore reduced to 0 volts and sensitive logic IC's will be saved. The fuse will st

Description Power supply with variable voltage and fixed current regulation made using the ubiquitous L200C regulator. Notes The versatile 5 pin L200C regulator offers both voltage and current regulation in a single package. The IC also features thermal shutdown and input over voltage protection up to 60 Vdc. The package is also available as L200CV which has straight pins for mounting onto a PCB. The above circuit has current limiting of 1 amp, hence Rsc = 0.45 ohm. The output voltage is variable from 2.85V to 36V. For voltages up to 36V then the input voltage, Vcc must be 40V. The supply voltage must always a few volts higher than the maximum output voltage. If you wanted to make a 9 Volt current limited PSU then the input voltage should be a minimum of 12 Volts. Maximum Power Dissipation The L200 has internal limiting to reduce the amount of heat dissipation. This happens when the internal junction temperature reaches 150 °C. The datasheet has a graph of the safe opera

Description: A variable power supply with adjustable voltage and current outputs made with the L200 regulator. Notes Using the versatile L200 voltage regulator, this power supply has independent voltage and current limits. The mains transformer has a 12volt, 2 amp rated secondary, the primary winding should equal the electricity supply in your country, which is 240V here in the UK. The 10k control is adjusts voltage output from about 3 to 15 volts, and the 47 ohm control is the current limit. This is 10mA minimum and 2 amp maximum. Reaching the current limit will reduce the output voltage to zero. Voltage and current regulation equations can be found at this page.

Description A simple 9 Volt 2 amp supply using a single IC regulator. Notes There is little to be said about this circuit. All the work is done by the regulator. The 78S09 can deliver up to 2 amps continuous output whilst maintaining a low noise and very well regulated supply. The circuit will work without the extra components, but for reverse polarity protection a 1N5400 diode is provided at the input, extra smoothing being provided by C1. The output stage includes C2 for extra filtering, if powering a logic circuit than a 100nF capacitor is also desirable to remove any high frequency switching noise.

Using a single 7812 IC voltage regulator and multiple outboard pass transistors, this power supply can deliver output load currents of up to 30 amps. The design is shown below: Notes The input transformer is likely to be the most expensive part of the entire project. As an alternative, a couple of 12 Volt car batteries could be used. The input voltage to the regulator must be at least several volts higher than the output voltage (12V) so that the regulator can maintain its output. If a transformer is used, then the rectifier diodes must be capable of passing a very high peak forward current, typically 100amps or more. The 7812 IC will only pass 1 amp or less of the output current, the remainder being supplied by the outboard pass transistors. As the circuit is designed to handle loads of up to 30 amps, then six TIP2955 are wired in parallel to meet this demand. The dissipation in each power transistor is one sixth of the total load, but adequate heat sinking is still require

Description A basic regulated 12 Volt power supply Notes This circuit above uses a 13 volt zener diode, D2 which provides the voltage regulation. Aprroximately 0.7 Volts are dropped across the transistors b-e junction, leaving a higher current 12.3 Volt output supply. This circuit can supply loads of up to 500 mA.This circuit is also known as an amplified zener circuit.

Specifications This kit provides a variable output power supply ranging from 1.2 to 15 V @ 3 A. It uses Low Dropout Positive Regulator LM1084 in TO220 package for delivering variable output voltage. Input - 18 VAC/DC Output - variable output from 1.2 ~ 15 V @ 3 A Regulated low ripple DC voltage Heatsink for regulator IC On board bridge rectifier to convert AC to DC LED indication at input of IC Zener trimmed band gap reference, current limiting and thermal shutdown (provided by IC feature) Power Battery Terminal (PBT) for easy input and output connection Onboard PCB mounted Potentiometer (POT) for varying the output voltage Filter capacitors for low ripple DC output Four mounting holes of 3.2 mm each PCB dimensions 46 mm x 58 mm Schematic Parts List PCB